The present invention relates generally to testing of wireless devices; and, more particularly, it relates to a shielded test system providing a common air interface for testing transmit and receive functionality of such devices.
The last few years have witnessed a worldwide proliferation of wireless communication devices. The ever-increasing number of these devices has resulted in an array of practical problems, particularly in the areas of deployment and testing. For example, wireless service providers often subsidize all or a portion of the cost of the mobile phones used by its network subscribers. If a particular phone does not perform to customer expectations, the service provider may attempt to return the phone to the manufacturer. If the manufacturer responds that the phone is operational, the service provider may be forced to absorb the subsidized portion of the cost of the phone. Accordingly, the service provider may desire to perform its own tests on a questionable phone in order to verify that it meets manufacturer performance specifications.
A number of such tests may be performed by the service provider. These tests generally verify the transmit and receive functionality of mobile phones, and often include signal degradation tests wherein a relatively low power test signal is provided to a phone to test its error handling capabilities in low-power environments. Also frequently performed are maximum transmission power level tests in which the transmission power of a phone under test is compared to that of a known good phone in order to verify that the levels are approximately the same. These types of tests may also be performed at the manufacturer""s site prior to shipment of phones to distributors.
To aid in testing, most mobile phones include a digital interface and/or test port for programming and testing certain of the electronic functionality. In addition, an analog test port is often provided for testing a phone""s transmit and receive functionality of a phone. In a typical mobile phone test environment, one or both of these test ports is physically coupled to a mobile/cellular radio test set via a direct cable connection. The phone under test may be enclosed in an RF-shielded environment in order to prevent ambient RF signals from interfering with the test data communicated over the direct cable connection.
However, prior test environments and methods for testing mobile phones suffer from a number of shortcomings. In particular, the aforementioned manufacturer tests bypass the antenna structure of the phone. Thus, the prior test solutions frequently do not detect problems that may exist in the electrical pathway between the antenna structure and other electrical components (e.g., transceiver amplifier circuitry).
In addition to bypassing the antenna structure, the direct connection method may also add up to several dB of loss to test measurements. Further, the cables that couple mobile phones to a test set are susceptible to breakage over time. Traditional test environments also do not permit repeatable and predictable testing of a wide variety of phone types having differing antenna structures.
Briefly, the present invention relates to a test system having a shielded enclosure and common air interface for testing the transmit and receive functionality of wireless communication devices. A test system according to the present invention provides improved fault coverage over prior solutions by permitting robust testing of the entire signal path of a mobile phone, including the antenna structure. The test system is configurable to accommodate a wide variety of phone types having differing heights and antenna structures.
In one embodiment of the invention, an RF-shielded enclosure having a test chamber is provided. The structure of the shielded enclosure impedes (i.e., reflects or absorbs) ambient RF energy from interfering with testing operations. The shielded enclosure may be lined with an RF absorbing material to improve test repeatability.
A test novel antenna structure is disposed in the test chamber for wirelessly communicating test signals to a device under test. The test antenna structure is designed to maximize coupling with the antenna(s) of one or more types of mobile phones or other wireless devices, while also minimizing variations in test measurements that might result from the particularized location of batteries or processing circuitry within such devices. The test antenna structure is coupled to an RF connector that provides a connection point for an external test set while maintaining shield integrity. The test set may function as a base-station simulator for use in testing all or a subset of the features of the device under test. A variety of exemplary test antenna configurations are disclosed.
The test antenna structure may be formed on a printed circuit board. In one such embodiment, the element(s) of the test antenna nearest the antenna of the device under test is formed on the side of the circuit board nearest the device under test. The remainder of the test antenna is formed on the opposite side of the printed circuit board to minimize any dependence of test measurements on battery location. A clamp assembly is also disposed in the test chamber for maintaining a device under test in a repeatable communicative relationship with the test antenna.
By providing for wireless communication of test signals with minimal transmission losses, a test system according to the present invention is able to test the entire signal path of a mobile phone, including the antenna, in a repeatable manner. In addition to mobile phones, the test system may be used for testing other types of wireless communication devices, as well as other devices requiring an RF-shielded test environment.